One method of rehabilitating defective pipe is to insert a soft liner within the pipe, and through various means cause it to harden against the host pipe. Hardening the soft liner results in a new pipe inside the defective pipe, and saves the inconvenience of digging up the old pipe to replace it. This new liner, however, blocks the entrance of previously-adjoining pipes. To re-open the entrance of previously-adjoining pipes, a remote cutting device is used to maneuver through the newly lined pipe and cut the liner at the intersection points.
Placement of the cutting device in the pipe is done in various ways using different methods of control and propulsion. Some use fiberglass push-rods, others use methods of self-propulsion, while another places all electric cables and air hoses inside a push-rod hose and uses a hose-pushing/pulling mechanism to motivate the robot into place.
Previous devices for cutting pipe liner have mostly focused on the larger pipes found in larger-diameter sewer “mains.” In these situations a cutting device does not need to navigate tight bends. However, smaller pipes, such as those inside buildings, or “laterals” joining buildings to a larger sewer “main” have been difficult to access with remote cutting devices.
Because of limited space, other cutting devices developed for the smaller-diameter “lateral” pipes include cutting bits that have a “mushroom” style as opposed to the more standard straight-flute designs. To cut effectively with a mushroom-style bit requires significant power. Most of the cutting devices having “mushroom” style cutting bits use low-power air-driven motors to perform the cutting action. The use of low-power air-driven motors requires increased cutting time and decreases cutting efficiency.
Additionally, in the previous devices, a standard way of holding the bit, such as via a collet or chuck, requires the shaft to be long, thereby limiting the ability of the device to perform in small diameter pipes. Alternatively, other prior art devices have cutting bits which thread directly onto a shaft and tighten with a pin spanner wrench on the bit and an open-end wrench on the shaft hex. This requires special tools to be available to change bits.
A cutting device must be able to maneuver tight bends in small-diameter pipe, and still be able to generate enough power to cut the liner in a timely manner once the location is reached. It would, therefore, be beneficial to provide a remote cutting device which can be placed into small diameter pipes and which can be operated through ninety degree bends and the like. It would also be beneficial to provide a cutter assembly which is powered by hydraulics, thereby allowing the cutting head to have sufficient power to perform in a small space.